The search engines strive to provide the best results for a search. The searcher is looking for something specific. Do you provide what the searcher is looking for?
If the search engines believe you provide relevant, quality information relevant to a search query they will list your site highly. If they find inbound links from related sites they will increase your ranking. There are dozens, perhaps hundreds of other factors the search engine use to rank your sites.
SEO is the process of providing users and search engines with a combination of all factors the search engines use to rank your sites.
It all starts with a good keyword research campaign. If you haven't done your keyword research, or you have used a free (haphazard) keyword service you probably need to find winnable keywords.
There is simply too much to cover in a forum post with the little information you provide. Start with learning on-page optimization, then link building, then...
The list seems endless when you are starting out.